On 03/09/2021 08:02, LacaK via fpc-pascal wrote:
>> I have code in C like this:
>> E1 << E2
>> If E1 is of unsigned type then "The value of E1 << E2 is E1
>> left-shifted E2 bit positions; vacated bits are zero-filled. If E1 has
>> an unsigned type, the value of the result is E1 × 2^E2, reduced
After 35 years of Pascal experience I would urgently recommend NOT to trust any
automatic type conversion in the case of shift operators. Alteady Turbo Pascal
failed here on x386 architectures. Force input and output variables to a
certain data type before you use the shift operator.
Just my
I made a few tests on Ubuntu 64 bits (arch x86_64) with variations on a
small test program:
var
E2: Byte= 3;
E1: LongWord= 1;
E: QWord;
begin
E:= (1000*E1) shl E2;
writeln( 'E2', E2);
writeln( 'E1', E1);
writeln( 'E', E);
end.
In the assembly window, shl is computed
Can we say that in Pascal the result of:
E1 shl E2
is of same type as E1 ?
(so if E1 is LongWord then result is LongWord also?)
What if there is an expression on left side:
(E1*x) shl E2
Will E1*x promote to 64 bits (on 64 bit target)?
See documentation on
On Fri, Sep 3, 2021 at 8:02 AM LacaK via fpc-pascal <
fpc-pascal@lists.freepascal.org> wrote:
> Can we say that in Pascal the result of:
>E1 shl E2
> is of same type as E1 ?
> (so if E1 is LongWord then result is LongWord also?)
>
> What if there is an expression on left side:
>(E1*x) shl
Can we say that in Pascal the result of:
E1 shl E2
is of same type as E1 ?
(so if E1 is LongWord then result is LongWord also?)
What if there is an expression on left side:
(E1*x) shl E2
Will E1*x promote to 64 bits (on 64 bit target)?
-Laco.
Hello *,
I have code in C like this:
E1 <<
Hello *,
I have code in C like this:
E1 << E2
If E1 is of unsigned type then "The value of E1 << E2 is E1 left-shifted
E2 bit positions; vacated bits are zero-filled. If E1 has an unsigned
type, the value of the result is E1 × 2^E2, reduced modulo one more than
the maximum value
